Projection display

ABSTRACT

An optical module includes a polarized-light separation device configured to separate first and second polarized components of incident light, a light valve configured to receive at least the first polarized component, and output at least a portion of the received light to the polarized-light separation device. The optical module further includes an imaging device disposed at a position that is at least substantially optically conjugated with the light valve, and as optical member positioned and configured to remove at least a portion of the second polarized component of the incident light before reaching the image pickup device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP2013-174728 filed Aug. 26, 2013, and Japanese PriorityPatent Application JP2014-32742 filed Feb. 24, 2014, the entire contentsof each of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a projection display having an imagepickup function.

BACKGROUND ART

In recent years, in units such as smartphones and tablet terminals, pageturning and scaling of images displayed on a screen, which are performedin response to pointing operation through intuition of a person, havebeen enabled by use of a touch panel. Meanwhile, displays that displayan image by projecting the image on a screen have been known asprojectors for a long time.

CITATION LIST Patent Literature

[PTL 1]

JP 2013-3859A

[PTL 2]

JP 2007-52218A

[PTL 3]

JP 2003-44839A

SUMMARY Technical Problem

In recent years, like tablet terminals etc., projectors have also beenexpected to accept pointing operation of a projected image, in a mannersimilar to operation on a touch panel by a hand through intuition of aperson. In particular, hand-held-type small projectors, which haveappeared on the market in recent years, have been expected to acceptpointing operation of an image projected in a projection area of about20 inches to 30 inches. However, in this type of projector, a touchpanel is not incorporated in a screen, a wall, or the like where animage is projected and therefore, it is necessary to detect operation bya hand, through use of other means. Besides this approach, in someprojectors, an image is allowed to be moved by operating a wirelessremote controller or the like. However, small projectors themselves aresmall in size and therefore, operation through a wireless remotecontroller or the like is not smart.

PTL 1 has proposed a unit that enables pointing operation of an image ina form of covering a projection area, by combining a projection unitwith a detection unit that detects operation (a gesture) performed by ahand. However, in the unit proposed by PTL 1, a projection section and adetection section are separate and therefore, the size of the entiresystem tends to be large. In addition, besides becoming large in size,there is such a drawback, concerning a configuration etc. of relativeposition coordinates between a projection area and a detection area,that it is necessary to perform calibration operation with accuracy. Theaccuracy of this calibration is important because this accuracy directlyaffects accuracy of the pointing operation and therefore, it isnecessary to perform the calibration for all parts of a screen, which iscomplicated.

PTL 2 and PTL 3 have each proposed a unit in which an image pickupfunction is added to a projector. In the unit proposed by PTL 3, a lightflux from a light source such as an extra-high pressure mercury lamp isincident on a polarization conversion device in which the light flux isconverted into a specific polarized component, and this polarizedcomponent is guided to a light valve. However, in this type ofpolarization conversion device, a component not being converted into thespecific polarized component is incident on an image pickup devicewithout traveling to the light valve, so that illumination light forprojection adversely affects image pickup. A polarization conversiondevice dedicated to image pickup may be added to avoid this situation.However, this increases the size of a projection lens and therefore isnot practical. In contrast, in the unit proposed by PTL 2, adverseeffects of illumination light are prevented, by turning off illuminationlight for projection when image pickup is performed, without adding apolarization conversion device dedicated to image pickup. However, sincethe illumination light is turned off in the image pickup, if isdifficult to secure sufficient brightness necessary for the imagepickup, for example, when the unit is used in a dark externalenvironment. Therefore, there are constraints in use, as a unitfrequently used in a dark external environment like a projector.

It is desirable to provide a projection display capable of easilyachieving detection of an object on or in proximity to a projectionplane with high accuracy.

Solution to Problem

In an embodiment, an optical module includes a polarized-lightseparation device configured to separate first and second polarizedcomponents of incident light, a light valve configured to receive atleast the first polarized component, and output at least a portion ofthe received light to the polarized light separation device. The opticalmodule further includes an imaging device disposed at a position that isat least substantially optically conjugated with the light valve, and anoptical member positioned and configured to remove at least a portion ofthe second polarized component of the incident light before reaching theimage pickup device.

In another embodiment, an optical system includes: an optical moduleincluding a polarized-light separation device configured to separatefirst and second polarized components of incident light; a light valveconfigured to receive at least the first polarized component, and outputat least a portion of the received light to the polarized-lightseparation device; an imaging device disposed at a position that is atleast substantially optically conjugated with the light valve; and anoptical member positioned and configured to remove at least a portion ofthe second polarized component of the incident light before reaching theimage pickup device; and an image processing section configured toprocess image data received by the image pickup device.

In another embodiment, a detection method includes: separating first andsecond polarized components of incident light with a polarized-lightseparation device; receiving with a light valve at least the firstpolarized component, and outputting at least a portion of the receivedlight to the polarized-light separation device; projecting an image,based on at least a portion of the modulated light, in a projection pathtoward a projection area; receiving with an imaging device at leastportions of detection light that is incident from the projection areaafter the detection light interacts with the polarized-light separationdevice; and detecting, based on image processing by the image device, aposition of the object that is positioned in the projection path,wherein at least a portion of the second polarized component of theincident light is removed by an optical member before reaching the imagepickup device.

In another embodiment, an optical module includes a polarized-lightseparation device configured to separate first and second polarizedcomponents of incident light, a light valve configured to receive atleast the first polarized component, and output at least a portion ofthe received light to the polarized-light separation device, an imagingdevice disposed at a position that is at least substantially opticallyconjugated with the light valve, and an optical member positioned infront of the polarized-light separation device.

Advantageous Effects of Invention

According to the projection display of the above-described embodiment ofthe present disclosure, the image pickup device is disposed at theposition optically conjugated with the light valve, and the polarizedcomponent unnecessary for object detection is reduced by disposing theoptical member at an appropriate position. Therefore, object detectionwith high accuracy is readily achievable. It is to be noted that,effects are not limited to that described here, and may be any ofeffects described in the present disclosure.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are provided toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram illustrating an example of an overallconfiguration of a projection display according to a first embodiment ofthe present disclosure.

FIG. 2 is a cross-sectional diagram illustrating a main partconfiguration of the projection display according to the firstembodiment, together with a state and a proportion of light incident oneach of a light valve and an image pickup device.

FIG. 3 is an explanatory diagram schematically illustrating a concept ofimage display and object detection.

FIG. 4 is a cross-sectional diagram illustrating a main partconfiguration of a projection display according to a first modificationof the first embodiment, together with a state of light incident on eachof a light valve and an image pickup device.

FIG. 5 is an explanatory diagram illustrating an example of control ofillumination light in a projection display according to a secondmodification of the first embodiment.

FIG. 6 is an explanatory diagram illustrating an example of control ofillumination light in a projection display according to a thirdmodification of the first embodiment.

FIG. 7 is a cross-sectional diagram illustrating a main partconfiguration of a projection display according to a fourth modificationof the first embodiment, together with a state of light incident on eachof a light valve and an image pickup device.

FIG. 8 is a configuration diagram illustrating as example of an overallconfiguration of a projection display according to a second embodiment.

FIG. 9 is a configuration diagram illustrating a state of the projectiondisplay according to the second embodiment, when viewed from a side-facedirection.

FIG. 10 is a cross-sectional diagram illustrating a configurationexample of a near-infrared-light emission section in the projectiondisplay according to the second embodiment.

FIG. 11 is a perspective view illustrating a first configuration exampleof a cylindrical array lens.

FIG. 12 is a perspective view illustrating a second configurationexample of the cylindrical array lens.

FIG. 13 is a cross-sectional diagram illustrating a main partconfiguration of the projection display according to the secondembodiment, together with a state of light incident on each of a lightvalve and an image pickup device.

FIG. 14 is a configuration diagram illustrating another configurationexample of the overall configuration of the projection display accordingto the second embodiment.

FIG. 15 is a cross-sectional diagram illustrating a first modificationof the main part configuration of the projection display according tothe second embodiment, together with a state of light incident on eachof the light valve and the image pickup device.

FIG. 16 is a cross-sectional diagram illustrating a second modificationof the main part configuration of the projection display according tothe second embodiment, together with a state of light incident on eachof the light valve and the image pickup device.

FIG. 17 is a cross-sectional diagram illustrating a first example of amain part configuration of a projection display according to a thirdembodiment, together with a state of light incident on each of a lightvalve and an image pickup device.

FIG. 18 is a cross-sectional diagram illustrating a second example ofthe main part configuration of the projection display according to thethird embodiment, together with a state of light incident on each of thelight valve and the image pickup device.

FIG. 19 is a cross-sectional diagram illustrating a third example of themain part configuration of the projection display according to the thirdembodiment, together with a state of light incident on each of the lightvalve and the image pickup device.

FIG. 20 is a cross-sectional diagram illustrating a first example of amain part configuration of a projection display according to a fourthembodiment, together with a state of light incident on each of a lightvalve and an image pickup device.

FIG. 21 is a characteristic diagram illustrating an example of spectrumdistribution of light incident on the image pickup device when abandpass filter is removed from a configuration, in the projectiondisplay illustrated in FIG. 20.

FIG. 22 is a cross-sectional diagram illustrating a second example ofthe main part configuration of the projection display according to thefourth embodiment, together with a state of light incident on each ofthe light valve and the image pickup device.

FIG. 23 is a characteristic diagram illustrating an example of spectrumdistribution of light incident on an image pickup device when aninfrared cut filter is disposed in a projection optical system.

FIG. 24 is a characteristic diagram illustrating an example ofwavelength characteristics of a bandpass filter.

FIG. 25 is a characteristic diagram illustrating an example of spectrumdistribution of light incident on the image pickup device in theprojection display illustrated in FIG. 20.

FIG. 26 is a block diagram illustrating a configuration example of asuppression section that controls variations in emission wavelength of adetection light-source section.

FIG. 27 is a first explanatory diagram for a placement position of avisible-light cut filter.

FIG. 28 is a second explanatory diagram for the placement position ofthe visible-light cut filter.

FIG. 29 is a first explanatory diagram for characteristics of apolarization beam splitter.

FIG. 30 is a second explanatory diagram for the characteristics of thepolarization beam splitter.

DESCRIPTION OF EMBODIMENTS

Some embodiments of the present disclosure will be described in detailwith reference to the drawings. It is to be noted that the descriptionwill be provided in the following order.

-   -   1. First embodiment (a projection display having a passive        detection function)        -   1.1 Configuration        -   1.2 Operation        -   1.3 Effects        -   1.4 Modifications of the first embodiment            -   1.4.1 First modification            -   1.4.2 Second modification            -   1.4.3 Third modification            -   1.4.4 Fourth modification    -   2. Second embodiment (a projection display having an active        detection function)        -   2.1 Configuration and functions        -   2.2 Modifications of the second embodiment        -   2.2.1 First modification        -   2.2.2 Second modification    -   3. Third embodiment (a projection display having a relay optical        system on an image pickup side)        -   3.1 First configuration example        -   3.2 Second configuration example        -   3.3 Third configuration example    -   4. Fourth embodiment (a projection display having a bandpass        filter)        -   4.1 Basic configuration example        -   4.2 Configuration example suitable for use of bandpass            filter        -   4.3 Other preferable configuration examples    -   5. Other embodiments

1. First Embodiment 1.1 Configuration

FIG. 1 illustrates an example of an overall configuration of aprojection display (a projector) according to a first embodiment of thepresent disclosure. FIG. 2 illustrates a main part configuration in theprojection display illustrated in FIG. 1, together with a state and aproportion of light incident on each of a light valve 21 and an imagepickup device 22. This projection display has a function of performingimage display, and also a function of performing passive objectdetection. FIG. 3 schematically illustrates a concept of the imagedisplay and the object detection performed by this projection display.

As illustrated in FIG. 1, this projection display includes anillumination section 1, the light valve 21, the image pickup device 22,a wire grid 27, a projection lens 24, a polarizer 25S, an imageprocessing section 26, and an the illumination control section 29. Thewire grid 27 serves as a polarized-light separation device, and thepolarizer 25S serves as a polarizing member.

The illumination section 1 emits illumination light L1 in a firstdirection Z1 towards the wire guide 27, as illustrated in FIG. 2. Theillumination section 1 includes a blue laser 11B, a green laser 11G, ared laser 11R, a first coupling lens 12B, a second coupling lens 12G,and a third coupling lens 12R. The illumination section 1 furtherincludes a drive optical device 14, a mirror 52, a first fly-eye lens151, a second fly-eye lens 152, a first condensing lens 161, a secondcondensing lens 162, a third condensing lens 163, and a fourthcondensing lens 164.

The blue laser 11B is a laser light source emitting a blue laser beam.The green laser 11G is a laser light source emitting a green laser beam.The red laser 11R is a laser light source emitting a red laser beam.

The illumination control section 29 controls light emission of each of afirst light source (for example, the blue laser 11B), a second lightsource (for example, the green laser 11G), and a third light source (forexample, the red laser 11R). For example, the illumination controlsection 29 may control the light emission of each of the first to thethird light sources, in a field sequential scheme.

The second coupling lens 12G is a lens used to collimate (provideparallel light of) the green laser beam emitted from the green laser11G, and to couple the collimated beam to a first dichroic prism 131.Similarly, the first coupling lens 12B is a lens used to collimate theblue laser beam emitted from the blue laser 11B, and to couple thecollimated beam to the first dichroic prism 131. Further, the thirdcoupling lens 12R is a lens used to collimate the red laser beam emittedfrom the red laser 11R, and to couple the collimated beam to a seconddichroic prism 132. It is to be noted that the respective incident laserbeams may be preferably collimated by the coupling lenses 12R, 12G, and12B (to be provided as parallel light).

The first dichroic prism 131 is a prism that selectively reflects thegreen laser beam incident through the second coupling lens 12G, whileselectively allowing the blue laser beam incident through the firstcoupling lens 12B to pass therethrough. The second dichroic prism 132 isa prism that selectively reflects the red laser beam incident throughthe third coupling lens 12R, while selectively allowing the blue laserbeam and the green laser beam emitted from the first dichroic prism 131to pass therethrough. Therefore, color composition (optical-pathsynthesis) for the red laser beam, the green laser beam, and the bluelaser beam is performed.

The drive optical device 14 is an optical device used to reduce specklenoise and interference fringes in the illumination light L1, anddisposed on an optical path between the first condensing lens 161 andthe second condensing tens 162. The drive optical device 14 may becapable of reducing the speckle noise and the interference fringes inthe illumination light L1, by, for example, changing a state of apassing light flux, by having micro vibration in a direction along theoptical path or a direction orthogonal to the optical axis.

The first fly-eye lens 151 and the second fly-eye lens 152 are each anoptical member (an integrator) with a plurality of lensestwo-dimensionally disposed on a substrate, and spatially divides theincident light flux according to an array of the plurality of lenses, toemit the divided light flux. The first fly-eye lens 151 is disposed onan optical path between the second dichroic prism 132 and the firstcondensing lens 161. The second fly-eye lens 152 is disposed on anoptical path between the second condensing lens 162 and the thirdcondensing lens 163. In-plane light quantity distribution of theillumination light L1 is equalized by the first fly-eye lens 151 and thesecond fly-eye lens 152.

The mirror 52 is disposed on an optical path between the firstcondensing lens 161 and the drive optical device 14. The firstcondensing lens 161 is a lens that condenses an outgoing beam from thefirst fly-eye lens 151, so that the condensed bean is incident on thedrive optical device 14 through the mirror 52. The second condensinglens 162 is a lens that condenses an outgoing beam from the driveoptical device 14, so that the condensed beam is incident on the secondfly-eye lens 152.

The third condensing lens 163 and the fourth condensing lens 164 areeach a lens that condenses an outgoing beam from the second fly-eye lens152, so that the condensed beam is emitted as the illumination light L1towards the wire grid 27.

The wire grid 27 may be a grid provided by, for example, forming a metalgrid with narrow spacing on a glass substrate. On the wire grid 27, theillumination light L1 from the first direction Z1 is to be incident. Thelight valve 21 is disposed in a second direction Z2. The polarizer 25Sand the image pickup device 22 are disposed in a third direction Z3. Theprojection lens 24 is disposed in a fourth direction Z4.

The wire grid 27 is a polarized-light separation device that separatesthe incident light into a first polarized component (for example, aP-polarized component) and a second polarized component (for example, anS-polarized component), and allows the polarized components to travel inrespective directions different from each other. The wire grid 27selectively reflects a specific first polarized component, andselectively allows a specific second polarized component to passtherethrough. For example, as illustrated in FIG. 2, the wire grid 27may emit (reflect) much of a P-polarized component Lp1 in the seconddirection Z2, and also emit (allow passage of) much of an S-polarizedcomponent Ls1 is the third direction Z3. The P-polarized component Lp1and the S-polarized component Ls1 are included in the illumination lightL1 incident from the first direction Z1. Further, as illustrated is FIG.2, the wire grid 27 may emit (reflect) much of a P-polarized componentLp3 in the third direction Z3. The P-polarized component Lp3 is includedin detection light L2 incident from a direction opposite to the fourthdirection Z4.

The light valve 21 may be, for example, a reflection-type liquid crystaldevice such as Liquid Crystal On Silicon (LCOS). For example, asillustrated in FIG. 2, the light valve 21 may modulate, based on imagedata, the first polarized component (for example, the P-polarizedcomponent Lp1) included in the illumination light L1 and incident fromthe second direction Z2 through the wire grid 27. Further, the lightvalve 21 emits this modulated light to the fourth direction Z4 throughthe wire grid 27. From the light valve 21, for example, an S-polarizedcomponent Ls2 whose state of polarization is turned from a state ofpolarization at incident time may be emitted as the modulated light, asillustrated in FIG. 2. It is to be noted that, in the light valve 21, itis possible to perform black display by returning the incidentP-polarized component Lp1 remaining in the same state of polarization,to the wire grid 27.

The projection lens 24 projects the modulated light emitted from thelight valve 21 and incident from the fourth direction Z4 through thewire grid 27, on a projection plane 30A of a screen 30. Further, asillustrated in FIG. 2, the detection light L2 is incident on theprojection lens 24, from a direction opposite to a traveling directionof the modulated light. The projection lens 24 is a projection opticalsystem used to project an image, and also serves as an image-formationoptical system for the object detection.

The image pickup device 22 is configured of a solid-state image pickupdevice such as a complementary metal-oxide semiconductor (CMOS) and acharge coupled device (CCD). The image pickup device 22 is disposed at aposition optically conjugated with the light valve 21. To be morespecific, when the light valve 21 is a reflection-type liquid crystaldevice, a display surface (a liquid crystal surface) on which an imageis to be created, and an image pickup surface of the image pickup device22, are disposed at positions optically conjugated with each other. Asillustrated in FIG. 2, the detection light L2 from the third directionZ3 is incident on the image pickup device 22, through the projectionlens 24 and the wire grid 27.

The polarizer 25S is a polarizing member that is one of optical membersthat reduce the second polarized component included in the illuminationlight L1. The polarizer 25S is disposed between the image pickup device22 and the wire grid 27. The polarizer 25S removes the second polarizedcomponent (for example, the S-polarized component) included in theincident light. As illustrated in FIG. 2, the polarizer 25S removes, asthe second polarized component, at least the S-polarized component Ls1included in the illumination light L1 and incident through the wire grid27.

As illustrated in FIG. 3, the image processing section 26 may detect,based on a result of image picked up by the image pickup device 22, forexample, a position P1 of a feature point of an indicator (an object) 71such as a finger of a person and a pointer, in a fashion of associatingthe position P1 with coordinates in a projected image V2 on theprojection plane 30A. A position of a fingertip of a person isillustrated as an example of the feature point in FIG. 3, but thefeature point is not limited to this example. The center of gravity of afinger of a person, the center of gravity of a hand, or the like may beappropriately selected.

1.2 Operation

In this projection display, as illustrated in FIGS. 1 and 3, imageinformation V1 formed at the light valve 21 is projected on theprojection plane 30A of the screen 30 by the projection lens 24, anddisplayed as the projected image V2 by being enlarged. Further, thisprojection display may detect by using the image pickup device 22, theposition of an object on the projection plane 30A, for example, theposition P1 of the feature point of the indicator (the object) 71 suchas a finger of a person and a pointer. The image pickup device 22 picksup an image of an area substantially the same as a projection area 31 onthe projection plane 30A, as an image-pickup area 32.

In this projection display, the polarized component of the illuminationlight L1 is allowed to be adjusted to become dominant, by using thelaser light sources in the illumination section 1. Specifically, thefirst polarized component may be preferably 99% or more, and may be morepreferably 99.5% or more. Here, as the first polarized component to bemade dominant, either the S-polarized component Ls1 or the P-polarizedcomponent Lp1 may be selected to match with characteristics of thepolarization conversion device. However, in either case, it is difficultto make the second polarized component become completely zero.

Here, an example of characteristics of the wire grid 27 is provided inTable 1. It is to be noted that Tp indicates transmittance of theP-polarized component, and Ts indicates transmittance of the S-polarizedcomponent. Rp indicates reflectance of the P-polarized component, and Rsindicates reflectance of the S-polarized component.

[Table 1]

When the first polarized component is the P-polarized component and thesecond polarized component is the S-polarized component, the wire grid27 reflects much of the P-polarized component and allows much of theS-polarized component to pass therethrough, as provided in Table 1.Therefore, for example, as illustrated in FIG. 2, 99.5% of theillumination light L1 is provided as the P-polarized component Lp1 thatis dominant, and the remaining 0.5% is provided as the S-polarizedcomponent Ls1. The wire grid 27 reflects much of the dominantP-polarized component Lp1, which is then emitted towards the light valve21. The S-polarized component Ls1 incident on the light valve 21 ismodulated (turned) by the light valve 21 to be the S-polarized componentLs2 as the modulated light. The S-polarized component Ls2 is thenincident on the projection lens 24 through the wire grid 27. TheS-polarized component Ls2, which is the modulated light, is projected asthe projected image V2 on the projection plane 30A of the screen 30through the projection less 24, as illustrated in FIG. 3.

In this projection display, the image pickup device 22 is disposed atthe position optically conjugated with the light valve 21. In addition,the projection lens 24 serves as the projection optical system forprojection of an image, and also serves as the image-formation opticalsystem for the object detection. Therefore, as illustrated in FIG. 3, animage of the same area as the projection area 31 is allowed to be pickedup as the image-pickup area 32, by the image pickup device 22. The lightvalve 21 and the image pickup device 22 are at the conjugate positions.Therefore, the position P1 of the feature point of the indicator 71 suchas a finger of a person and a pointer on the projection plane 30A isallowed to be overlaid on the projected image V2 through the projectionlens 24, and to be monitored. Further, for example, in the imageprocessing section 26, pointing operation of the projected image V2 isallowed by performing image processing on the shape of the indicator 71,and detecting the coordinates of the position P1 of the feature point ofthe indicator 71. At this moment, an arbitrary coordinate position inthe projection area 31 and a coordinate position in the image-pickuparea 32 are in a one-to-one correspondence. Therefore, the coordinatesof a detection position P2 on the image pickup device 22 sidecorresponds to the coordinates of the position P1 of the feature pointof the indicator 71. It is to be noted that the indicator 71 may beprovided as each of two or more indicators, so that, for example, it ispossible to detect coordinates of a fingertip of each of both hands. Bythus using the position of the feature point of the detected indicator71, intuitive operation is allowed to be performed, as if a touch panelis incorporated in the projected image V2 of the projector.

Next, functions of the polarizer 25S will be described with reference toFIG. 2. The detection light L2 incident on the wire grid 27 issubstantially natural light, and an S-polarized component Ls3 and theP-polarized component Lp3 are each included as a polarized componentthereof by 50%. The wire grid 27 reflects much of the P-polarizedcomponent Lp3 in the third direction Z3. When the polarizer 25S isassumed to remove the S-polarized component, almost all the reflectedP-polarized component Lp3 reaches the image pickup device 22. Further,of the illumination, light L1 incident on the wire grid 27, theS-polarized component Ls1 is emitted in the third direction Z3. TheS-polarized component Ls1 becomes a noise component with respect to thedetection light L2, and when the S-polarized component Ls1 is incidenton the image pickup device 22, a signal to noise (S/N) ratio at the timeof detection becomes small, which reduces detection accuracy. It ispossible to enhance the detection accuracy, by increasing the S/N ratio,by disposing the polarizer 25S to remove the S-polarized component Ls1.

Here, a quantity of light incident on each of the light valve 21 and theimage pickup device 22 when the wire grid 27 is used will be discussed.Assume that a small display is used as the projection display, and imagedisplay is performed at about 100 lm. An area where object detection isdesired may be, for example, about 30 cd/m², in a situation where thereis indoor lighting. Then, for example, illumination of light incident onthe image pickup device 22 after passing through the projection lens 24may be about a few lux. Meanwhile, basically, the illumination light L1has the polarized light adjusted to the P-polarized component andtherefore is reflected by the wire grid 27, and then travels to thelight valve 21. However, although the light flux of the illuminationlight L1 also has the adjusted polarized component because the lightflax is a laser beam, about 0.5% of a polarized component (theS-polarized component Ls1) not to be used is included.

Of the light of the S-polarized component Ls1, 15% passes through thewire grid 27, and has three-or-more-digit illumination, which is about3000 lux, when reaching the image pickup device 22. Therefore, althoughinformation about illumination of a few lux is desired to be detected onthe detection side, some thousands lux of unnecessary light exists on alight transmission side. Hence, it is difficult to read a change inluminance of only the desired information, and information about achange in position. It is possible to address such a disadvantage, byremoving the S-polarized component Ls1 by providing the polarizer 25S.

1.3 Effects

As described above, according to the present embodiment, the imagepickup device 22 is disposed at the position optically conjugated withthe light valve 21, and the polarizer 25S is disposed as one of theoptical members at an appropriate position, to remove the polarizedcomponent that becomes unnecessary at the time of the object detection.Therefore, it is possible to achieve object detection with high accuracyeasily. It is to be noted that any effect described herein is a mereexample and non-limiting, and the present technology may provide othereffects. This also applies to other embodiments and modifications thatwill be described below.

1.4 Modifications of First Embodiment

(1.4.1 First Modification)

FIG. 4 illustrates a main part configuration of a projection displayaccording to a first modification of the first embodiment, together witha state of light incident on each of the light valve 21 and the imagepickup device 22. In the first modification, a polarization beamsplitter 23 is provided as the polarized-light separation device, inplace of the wire grid 27. In addition, in the first modification, apolarizer 25 that removes the P-polarized component is provided in placeof the polarizer 25S that removes the S-polarized component.

In the wire grid 27 in the configuration of FIG. 2, the first polarizedcomponent is the P-polarized component, the second polarized componentis the S-polarized component, the wire grid 27 reflects the P-polarizedcomponent, and allows the S-polarized component to pass therethrough.However, the polarization beam splitter 23 has a characteristic oppositeto this characteristic.

The polarization beam splitter 23 has four optical surfaces. Here, twosurfaces facing each other in a horizontal direction in FIG. 4 areprovided as a first optical surface and a third optical surface.Further, two surfaces facing each other in a vertical direction in FIG.4 are provided as a second optical surface and a fourth optical surface.As illustrated in FIG. 4, on the first optical surface of thepolarization beam splitter 23, the illumination light L1 is incidentfrom the first direction Z1. With respect to the second optical surfaceof the polarization beam splitter 23, the light value 21 is disposed inthe second direction Z2. With respect to the third optical surface ofthe polarization beam splitter 23, the polarizer 25 and the image pickupdevice 22 are disposed in the third direction Z3. With respect to thefourth optical surface of the polarization beam splitter 23, theprojection lens 24 is disposed in the fourth direction Z4.

The polarization beam splitter 23 is a polarized-light separation devicethat separates the incident light into a first polarized component (forexample, the S-polarized component) and a second polarized component(for example, the P-polarized component), and allows these polarizedcomponents to travel in the respective directions different from eachother. The polarization beam splitter 23 selectively reflects a specificfirst polarized component, and selectively allows a specific secondpolarized component to pass therethrough. For example, as illustrated inFIG. 4, the polarization beam splitter 23 may emit (reflect) almost allthe S-polarized component Ls1 in the second direction Z2, and emit(allow passage of) almost all the P-polarized component Lp1 in the thirddirection Z3. The S-polarized component Ls1 and the P-polarizedcomponent Lp1 are included in the illumination light L1 incident fromthe tint direction Z1. Further, as illustrated in FIG. 4, thepolarization beam spinier 23 may emit (reflect) almost all theS-polarized component Ls3 in the third direction Z3. The S-polarizedcomponent Ls3 is included in the detection light L2 incident from thedirection opposite to the fourth direction Z4.

When the first polarized component is the S-polarized component and thesecond polarized component is the P-polarized component, thepolarization beam splitter 23 reflects much of the S-polarizedcomponent, and allows much of the P-polarized component to passtherethrough. Therefore, for example, as illustrated in FIG. 4, 99.5% ofthe illumination light L1 may be provided as the S-polarized componentLs1 that is dominant, and the remaining 0.5% may be provided as theP-polarized component Lp1. As illustrated in FIG. 4, the polarizationbeam splitter 23 reflects almost all the dominant S-polarized componentLs1, and emits the reflected S-polarized component Ls1 towards the lightvalve 21. The S-polarized component Ls1 incident on the light valve 21is modulated (turned) by the light valve 21 to be the modulated lightthat is the P-polarized component Lp2. The P-polarized component Lp2 isthen incident on the projection lens 24 through the polarization beamspinier 23. The P-polarized component Lp2, which is the modulated light,is projected on the projection plane 30A of the screen 30 through theprojection lens 24 as the projected image V2, as illustrated in FIG. 3.

On the other hand, the detection light L2 incident on the polarizationbeam splitter 23 is substantially natural light, and the S-polarizedcomponent Ls3 and the P-polarized component Lp3 are each included as apolarized component thereof by 50%. The polarization beam splitter 23reflects almost all the S-polarized component Ls3 in the third directionZ3. Assuming that the polarizer 25 removes the P-polarized component,almost all the reflected S-polarized component Ls3 reaches the imagepickup device 22. On the other hand, of the illumination light L1incident on the polarization beam splitter 23, the P-polarized componentLp1 is emitted in the third direction Z3. The P-polarized component Lp1becomes a noise component with respect to the detection light L2, andwhen the P-polarized component Lp1 is incident on the image pickupdevice 22, the S/N ratio at the time of detection becomes small, whichreduces detection accuracy. It is possible to enhance the detectionaccuracy by increasing the S/N ratio, by disposing the polarizer 25 toremove the P-polarized component Lp1.

As illustrated in Table 1 and FIG. 2, in the case of using the wire grid27, projection light (the S-polarized component Ls2) is 83%*75%*R withrespect to the P-polarized component Lp1 forming 99.5% of theillumination light L1, which is inferior to that in the case of usingthe polarization beam splitter 23. However, in the wire grid 27, thetransmittance of the P-polarized component is stably zero irrespectiveof conditions of an optical design. Therefore, this may be a designachieving a balance, to obtain a detection signal normally.

On the other hand, in the case of the polarization beam splitter 23,depending on a condition (an incident angle) of an optical design orperformance of a polarized-light separation film, the first polarizedcomponent may also be allowed to pass therethrough, although aproportion thereof is extremely small. Consideration is necessary forthis situation. Second and third modifications as well as a secondembodiment to be described below are effective at stably obtaining adetection signal, even in such a situation.

(1.4.2 Second Modification)

As described above, when the polarization beam splitter 23 is used asthe polarized-light separation device, the S-polarized component Ls1 ofthe passing illumination light L1 may reach the image pickup device 22.Therefore, in the second modification, when the polarization beamsplitter 23 is used as the polarized-light separation device, theS-polarized component Ls1 of the illumination light L1 is removed by amethod of turning off the light source of me illumination section 1, atthe time of detection, as illustrated in FIG. 5. Usually, a projectorcauses light sources to perform temporally-sequential light emission inorder of RGBRGB, by using a field sequential method, as illustrated inFIG. 5.

In the configuration example of FIG. 1, the illumination control section29 controls light emission of the blue laser 11B, the green laser 11G,and the red laser 11R by using the field sequential scheme, as the firstto the third light sources, respectively. When a frame rate of an imageto be projected is 60 fps, this set of RGB is repeated 60 times persecond. The illumination from the light source on the image pickupdevice 22 is allowed to be zero, by performing complete turning-off atone of the 60 times. In this case, as illustrated in FIG. 5, forexample, the illumination control section 29 may control the lightemission of the first to the third light sources, so that a first frame1 to a 59th frame 59 form an image projection frame (a first lightemission period) in which light is emitted in illumination necessary forimage projection. Further, the illumination control section 29 maycontrol the light emission of the first to the third light sources, sothat a 60th frame 60 forms a signal detection frame (a second lightemission period). In this case, brightness as the projector is merely59/60 and therefore, the brightness is not significantly affected. Inaddition, shutter time is 1/60 per second, which is sufficient asimage-pickup time on the detection side and therefore, sufficientsensitivity is achieved by using an ordinary CMOS or the like. Hence, itis possible to detect where the position P1 of the feature point of theindicator 71 such as a finger of a person and a pointer is, by using apassive method.

(1.4.3 Third Modification)

FIG. 6 illustrates an example of control of illumination light in aprojection display according to a third modification of the firstembodiment. In the above-described second modification, the lightsources are turned off (the illumination is made to be zero) in thesignal detection frame (the second light emission period). However, inthe third modification, light emission is controlled to decreaseillumination in a range in which the illumination does not become zero.To be more specific, the illumination control section 29 controls thelight emission of the first to the third light sources as follows. Inthe signal detection frame (the second light emission period), theillumination is decreased in the range in which the illumination doesnot become zero, as compared with the illumination in the imageprojection frame (the first light emission period). According to thismethod, even when the projection display is used in an almost completelydark room, it is possible to detect the position P1 of the feature pointof the indicator 71, by using the illumination light in the reducedillumination.

(1.4.4 Fourth Modification)

FIG. 7 illustrates a main part configuration of a projection displayaccording to a fourth modification of the first embodiment, togetherwith a state of light incident on each of the light valve 21 and theimage pickup device 22. The fourth modification is similar to theconfiguration in FIG. 4, except that the polarizer 25 is disposedbetween the illumination section 1 and the polarization beam splitter23.

2. Second Embodiment 2.1 Configuration and Functions

FIG. 8 illustrates an example of an overall configuration of aprojection display according to the second embodiment. FIG. 9illustrates a state of this projection display when viewed from aside-face direction. FIG. 10 illustrates a configuration example of anear-infrared-light emission section 40 in this projection display. FIG.13 illustrates a main part configuration of this projection display,together with a state of light incident on each of the light valve 21and the image pickup device 22. It is to be noted that, in the presentembodiment, a case in which the polarization beam splitter 23 is used asthe polarized-light separation device will be described as an example.

The present embodiment relates to a projection display having a functionof actively performing object detection, by using near-infrared light.In the method of passive object detection by the above-described firstembodiment, a simple configuration is provided, but a load of the imageprocessing may be large. It may be necessary to perform processing onthe position, shape, coordinate information, etc. of a finger or thelike, in real time. According to the present embodiment, it is possibleto ease such processing. In the following, a configuration assuming thata short focus type is used as the projection display will be described.

This projection display includes the near-infrared-light emissionsection 40 below a main body section 100 as illustrated in FIGS. 8 and9. The projection plane 30A may be, for example, a flat floor. Thenear-infrared-light emission section 40 is a detection light source thatemits a detection near-infrared light 41 as non-visible light fordetection. The near-infrared-light emission section 40 emits thedetection near-infrared light 41, so that at least the projection area31 on the projection plane 30A is covered by the detection near-infraredlight 41 from a predetermined height h. On the image pickup device 22,near-infrared scattering light La scattered by the indicator 71 isincident as detection light through the projection lens 24 and thepolarization beam splitter 23, as illustrated in FIG. 13. Thisprojection display further include a visible-light cut filter 28disposed between the polarization beam splitter 23 and the image pickupdevice 22, as illustrated in FIG. 13. The visible-light cut filter 28reduces a visible range to a few percent, depending on characteristics.

The near-infrared-light emission section 40 includes a near-infraredlaser 42, a collimator lens 43, and a cylindrical array lens 44, asillustrated in FIG. 10. The cylindrical array lens 44 includes aplurality of convex cylindrical leases arranged as illustrated in FIG.11. The cylindrical array lens 44 is disposed so that a generatrix 44Aof the cylindrical lens is directed to a surface perpendicular to theprojection plane 30A. It is to be noted that, in place of the convexcylindrical array lens 44, a cylindrical array lens 45 including aplurality of concave cylindrical lenses arranged as illustrated in FIG.12 may be used.

It is to be noted that, as illustrated in FIG. 14, for example, thisprojection display may have a configuration in which a detectionlight-source section 45 and a detection light-transmission section 46are incorporated as the near-infrared-light emission section 40, into anouter casing of the main body section 100. In this case, the main bodysection 100 may be installed so that a predetermined surface (a housingundersurface 47) of the outer casing is coplanar with the projectionplane 30A.

In this projection display, the projection lens 24 may be a super shortfocus lens in which a throw ratio is 0.38 or less. Here, the throw ratiomay be expressed as L/H, where a distance from the projection lens 24 tothe projection plane 30A is L, and a width of the protection area is H,as illustrated in FIGS. 8, 9, and 14.

In this projection display, as illustrated in FIGS. 8 and 9, a film-likenear infrared barrier (a detection field of non-visible light) may beprovided in the projection area 31, at the height h of a few millimetersto tens of millimeters from the projection plane 30A, for example, overa range of 2 nm to 3 mm in a height direction and covering theprojection area 31 in an area direction. In other words, thenear-infrared light may be so emitted as to cut across a light flux ofthe projection light at the height h from the projection plane 30A.Then, usually, since the projection plane 30A is flat, the film of theemitted near-infrared light travels straight without being blocked,unless an obstruction or the indicator 71 such as a finger and a pointeris present. Therefore, the film does not appear in the image pickupdevice 22 that monitors the projection plane 30A. In this state, when afinger or the like is brought a few millimeters in proximity to theprojection plane 30A, or an action such as touching the projection plane30A is taken, the light of the barrier is blocked by the finger andscatters at that point. The light scattering upon hitting the fingertravels in all directions, and a part of the light returns to an openingof the projection lens 24. This returning light reaches the image pickupdevice 22, after passing through the projection lens 24 and then passingthrough the polarization beam splitter 23. At this moment, the lightvalve 21 and the image pickup device 22 forming an image are disposed atthe conjugate positions. Therefore, bright-spot scattering pointsgenerated like dots on the projection plane 30A form an image on theimage pickup device 22, which image is formed at a position in a 1:1correspondence with the projected image. It is possible to detect theposition by doing so. In addition, the super short focus type has suchan advantage that it is easy to view a screen when performing operation,because the projection light passes in proximity to the projection plane30A and resists being blocked by a part of a body of a person performingthe operation.

Further, in this projection display, as illustrated in FIG. 13, thevisible-light cut filter 28 is further provided. Therefore, even whenthe polarization beam splitter 23 is used as the polarized-lightseparation device, it is possible to cut much of the illumination lightL1 incident on the image pickup device 22 side, without turning off thelight sources of the illumination section 1. This makes it possible toallow substantially only the detection light (the near-infraredscattering light La) to be incident on the image pickup device 22 side,and to enhance the detection accuracy by increasing the S/N ratio.

Here, an example of characteristics of the polarization beam splitter 23is provided in Table 2. It is to be noted that Tp indicatestransmittance of the P-polarized component, and Ts indicatestransmittance of the S-polarized component. Rp indicates reflectance ofthe P-polarized component, and Rs indicates reflectance of theS-polarized component.

[Table 2]

Here, as provided in Table 2, the polarization beam splitter 23 issuperior, in terms of the reflectance of the S-polarized component andthe transmittance of the P-polarized component. Therefore, asillustrated in FIG. 13, the projection light (the P-polarized componentLp2) is 98%*97%*R (R is reflectance of the light valve 21), with respectto the S-polarized component Ls1 that is 99.5% of the illumination lightL1. Hence, it is possible to use the projection light very effectively,without loss. Therefore, the polarization beam splitter 23 is suitablefor configuration of a bright projector. However, on the other hand,some transmittance of the S-polarized component also exists, which is0.05%. When pointing operation is performed, even if the polarizer 25 isdisposed in a state of cutting the P-polarized component of the lighttraveling towards the image pickup device 22 side, 99.5%*0.05% of theS-polarized component Ls1 of the illumination light L1 passing throughthe polarization beam splitter 23 is generated, besides the S-polarizedcomponent Ls3 of the detection light L2. When reaching the image pickupdevice 22 on the above-described condition, this component becomes aboutsome hundreds of lux of unnecessary light.

On the other hand, the illumination on the image pickup device 22 of thedetected near-infrared scattering light La depends on an output of thenear-infrared laser 42 and reflectance of the indicator 71, but isexperimentally some hundreds of lux in a state in which a laser outputis 100 mW. Therefore, even if the S-polarized component Ls1 serving atthe first polarized component passes through the polarization beamsplitter 23, it is possible to achieve a sufficient S/N ratio, by usingthe visible-light cut filter 28 and the polarizer 25. Specifically, thevisible-light cut filter 28 is provided between the illumination section1 and the image pickup device 22, to reduce the first polarizedcomponent to about 10 lux, and the P-polarized component Lp1 serving asthe second polarized component is reduced by the polarizer 25.

2.2 Modifications of Second Embodiment

(2.2.1 First Modification)

FIG. 15 illustrates a first modification of the main part configurationof the projection display according to the second embodiment, togetherwith a state of light incident on each of the light valve 21 and theimage pickup device 22. This first modification has a configurationsimilar to the configuration in FIG. 13, except that the polarizer 25 isdisposed between the illumination section 1 and the polarization beamsplitter 23.

(2.2.2 Second Modification)

FIG. 16 illustrates a second modification of the main part configurationof the projection display according to the second embodiment, togetherwith a state of light incident on each of the light valve 21 and theimage pickup device 22. This second modification has a configurationsimilar to the configuration in FIG. 13, except that the polarizer 25 isremoved from the configuration. Even when the polarizer 25 is removedfrom the configuration, it is possible to achieve a sufficient S/Nratio, for example, by disposing a plurality (for example, two) of thevisible-light cut filters 28. Both the P-polarized component Lp1 and theS-polarized component Ls1 of the illumination light L1 incident on theimage pickup device 22 are reduced by the visible-light cut filters 28.

3. Third Embodiment

The present embodiment relates to a projection display having a relayoptical system on the image pickup side. The projection displayaccording to the present embodiment further includes one or more relaylens groups each having positive power, between the image pickup device22 and the polarized-light separation device. In the following, theprojection display including the relay optical system in theconfiguration of the second embodiment will be taken as an example, hutthis projection display is also applicable to the configuration of thefirst embodiment.

3.1 First Configuration Example

FIG. 17 illustrates a first example of a main part configuration of aprojection display according to the present embodiment, together with astate of light incident on each of the light valve 21 and the imagepickup device 22. As illustrated in FIG. 17, a relay lens group 51 isprovided between the Image pickup device 22 and the polarization beamsplitter 23. The relay lens group 51 has positive power, and includes atleast one lens. When a focal length of the relay lens group 51 is “f”,the relay lens group 51 is disposed at a position of 2 f away from aconjugate plane 50 of the light valve 21, immediately behind thepolarization beam splitter 23. Further, the image pickup device 22 isdisposed at a position of 2 f away therefrom, so that it is possible toperform object detection substantially similar to object detection in acase in which the image pickup device 22 is disposed at the conjugateplane 50. It is possible to obtain positional flexibility, by forming aconjugate point at a distant position. Further, the relay lens group 51forms a one-side telecentric optical system in which substantialtelecentricity is provided between the relay lens group 51 and thepolarization beam splitter 23.

3.2 Second Configuration Example

FIG. 18 illustrates a second example of the main part configuration ofthe projection display according to the present embodiment, togetherwith a state of light incident on each of the light valve 21 and theimage pickup device 22.

In the configuration in FIG. 18, in place of the relay lens group 51 inthe configuration in FIG. 17, a first relay lens group 51A and a secondrelay lens group 51B are provided in this order from a side close to thepolarization beam splitter 23. A focal length fi of the second relaylens group 51B is smaller than a focal length fb of the first relay lensgroup 51A.

Using the first relay lens group 51A and the second relay lens group51B, a reduction optical system of a reduction magnification B (beta),which is B=fi/fb, is configured. Further, a relationship of Li>B*Lb issatisfied by an effective area Li of the image pickup surface of theimage pickup device 22 and an effective area Lb of the display surfaceof the light valve 21.

For example, a condition of 2 fi=fb is assumed. Also, the first relaylens group 51A may be disposed at a position of fb away from theconjugate plane 50 of the light valve 21, the second relay lens group51B may be disposed at a position of fb+fi away therefrom, and the imagepickup device 22 may be disposed at a position away only by fi from thesecond relay lens group 51B. In this case, the position of the imagepickup device 22 is equivalent to the conjugate plane 50 and in additionthereto, it is possible to form a 0.5× reduction optical system, so thatobject detection by using the image pickup device 22 of a small type isachievable. This provides a great advantage in terms of cost. The costof the image pickup device 22 is greatly influenced by the size of theimage pickup device 22. The cost of the light valve 21 and the imagepickup device 22, which are semiconductor components, is large inconfiguring a projector. Attempting to downsize such a component greatlycontributes to the cost. In addition, the first relay lens group 51A andthe second relay lens group 51B form a both-side telecentric opticalsystem, in which substantial telecentricity is provided between thefirst relay lens group 51A and the polarization beam splitter 23, andprovided between the second relay lens group 51B and the image pickupdevice 22.

3.3 Third Configuration Example

FIG. 19 illustrates a third example of the main part configuration ofthe projection display according to the present embodiment, togetherwith a state of light incident on each of the light valve 21 and theimage pickup device 22. Between the image pickup device 22 and thepolarization beam splitter 23, one or more reflecting mirrors eachhaving polarization-selectivity and wavelength-selectivity may bedisposed as a polarizing member. The reflecting mirror reflects, towardsthe image pickup device 22, the detection light incident through theprojection lens 24 and the polarization beam splitter 23. In theconfiguration example in FIG. 19, a hot mirror 52 havingpolarization-selectivity and wavelength-selectivity is disposed betweenthe first relay lens group 51A and the second relay lens group 51B.

Flexibility of placement is increased by extending the conjugate pointin a relay optical system. By forming a distance between the components,it is possible to achieve a folding optical system therebetween with thereflecting mirror or the like. This reflecting mirror not only increasesthe flexibility of placement, but also reduces components of thevisible-light cut filter 28 and the polarizer 25. By providing thereflecting mirror with such characteristics that the S-polarizedcomponent is reflected and the P-polarized component is allowed to passtherethrough, it is possible to cut the P-polarized component from theillumination section 1, the P-polarized component being an unnecessarylight component of light reaching the image pickup device 22. It is notnecessary to provide the polarizer 25 separately. Further, thereflecting mirror is allowed to also serve as the visible-light cutfilter 28, by providing the reflecting mirror with such spectralcharacteristics that visible wavelength region reflectance is reducedand only a near-infrared wavelength region is reflected, which is calleda hot mirror.

4. Fourth Embodiment

The present embodiment relates to a projection display having a functionof detecting an object by using near-infrared light, like the second andthe third embodiments. In the following, description of configurationsand functions similar to those of the second and the third embodimentswill be omitted as appropriate.

4.1 Basics Configuration Example

FIG. 20 illustrates a first example of a main part configuration of aprojection display according to the present embodiment together with astate of light incident on each of the light valve 21 and the imagepickup de vice 22. In the configuration example of FIG. 20, a both-sidetelecentric optical system including the first relay lens group 51A andthe second relay lens group 51B is formed between the image pickupdevice 22 and the polarization beam splitter 23, in a manner similar tothat of the configuration example illustrated in FIG. 18. It is to benoted that in the following, an optical system between the conjugateplane 50 of the light valve 21 and the image pickup device 22 will bereferred to as a detection optical system 80. Further, an optical systemcontributing to image display, except the detection optical system 80,will be referred to as a projection optical system 90.

In the configuration example in FIG. 20, in addition to the polarizer 25and the visible-light cut filter 28, a bandpass filter 81 is furtherprovided as an optical member used to reduce a light component becomingunnecessary at the time of object detection. The polarizer 25 isdisposed between the image pickup device 22 and the second relay lensgroup 51B. As described above in the second embodiment the polarizer 25suppresses arrival of the P-polarized component Lp1 serving as thesecond polarized component at the image pickup device 22, of theillumination light L1 incident on the polarization beam splitter 23. Thebandpass filter 81 and the visible-light cut filter 28 may be preferablydisposed between the polarization beam splitter 23 and the first relaylens group 51A, for a reason to be described later.

In the configuration example in FIG. 20, disposing the bandpass filter81 in an optical path of the detection optical system 80 is one offeatures in the projection display according to the present embodiment.In the projection display according to the present embodiment, thedetection near-infrared light 41 is emitted as non-visible light fordetection, from the near-infrared-light emission section 40 serving asthe detection light-source section, in a manner similar to that of thesecond embodiment (FIG. 8). On the detection, optical system 80, thenear-infrared scattering light La scattered by the indicator 71 isincident through the projection lens 24 and the polarization beamsplitter 23, as the detection light. The bandpass filter 81 allows onlylight in a predetermined passband width centering on a predeterminedemission wavelength, which is emitted by the detection light source, topass therethrough as light in a specific wavelength region. Thisincreases the S/N ratio with unnecessary light, thereby achievingstability of detection.

In the above-described second embodiment, since the near-infrared lightis used as the detection light and the visible light is used as thelight for image display, only the visible light is handled as the lightunnecessary for the detection. Therefore, as illustrated in FIGS. 13,16, etc., the unnecessary light is reduced at least by disposing thevisible-light cut filter 28. Actually, however, unnecessary light may bealso present, in a region other than the infrared wavelength region. Insuch a case, in the configuration of the second embodiment, it isdifficult to separate the near-infrared light desired to be detected andunnecessary infrared light not contributing to the detection. Therefore,when a quantity of unnecessary light is large, the detection light isburied in the unnecessary light, making it difficult to ensure asufficient S/N ratio and to perform stable detection. Even in such acase, it is possible to ensure a sufficient S/N ratio, by increasing adriving current of tire detection light source so that the quantity ofthe detection light becomes sufficiently larger than the quantity of theunnecessary light. However, this method may involve large powerconsumption and therefore application to a hand-held-type smallprojector may become unpreferable. Hence, in the present embodiment,there will be described a specific method used to perform stabledetection without increasing the power consumption, even when theunnecessary light in the infrared, wavelength region is large.

FIG. 21 illustrates an example of spectrum distribution of lightincident on the image pickup device 22, when the bandpass filter 81 isremoved from the configuration in the projection display illustrated inFIG. 20. In FIG. 21, a horizontal axis indicates the wavelength (nm),and a vertical axis indicates the light quantity (a.u. (arbitraryunit)). When the bandpass filter 81 is removed from the configuration,although depending on a film design and capturing efficiency of theinfrared region of the optical system, a ratio (an S/N ratio) between adetection signal and unnecessary light on the image pickup device 22 inthe last stage of the detection optical system 80 is about 1:10.Therefore, there is too much unnecessary light, and the detection signalis buried in noise, which makes the detection difficult. In the spectrumdistribution illustrated in FIG. 21, wavelength components of thedetection signal and the unnecessary light are included. In thisexample, since the visible-light cut filter 28 is provided, a componentof visible light of RGB for image display is not present. In thisexample, a laser beam of 785 nm is used as the detection light-sourcesection and therefore, a peak is at 785 nm as the detection light, andthis is a signal desired to be detected. However, around 785 nm,unnecessary light is intensely present in an infrared region of 700 nmto 1,100 nm at peak of 850 nm. Since this unnecessary infrared light ispresent, it is difficult to detect only 785 nm of the detection signal.The unnecessary infrared light received on the image pickup device 22 isa factor that lowers the S/N ratio. Since the same wavelength componentsare received by the image pickup device 22 at the same time, the S/Nratio is about 1:10 when each wavelength component is integrated.Therefore, the necessary detection signal is too weak, which makes thedetection difficult.

In the present embodiment, the following measures are taken to extractthe necessary detection signal from the above-described unnecessaryinfrared light.

Here, the unnecessary infrared light includes the following threecomponents.

1. A component included in natural light incident on the detectionoptical system 80 through the projection less 24

2. A component of an infrared region included in the RGB light source(the red laser 11R, the green laser 11G, and the blue laser 11B) of theillumination section 1 (FIG. 1)

3. A radiation component resulting when a visible light flux from theRGB light source of the illumination section 1 is incident on the lightvalve 21 and other optical component

About the above-described component 1, light (natural light) fromoutside is small in an environment where a projector is used andtherefore, it is less necessary to perceive this component as an issue.It is desirable to address the above-described components 2 and 3, oreventually only the above-described component 3.

Measures against, the described component 2 are as follows. Like aconfiguration example in FIG. 22, an infrared cut filter 82 that allowsvisible light to pass therethrough and reduces infrared light isprovided between the illumination section 1 and the polarization beamsplitter 23 in the projection optical system 90. For example, theinfrared cut filter 82 may be disposed to face a surface, on which theillumination light L1 is incident, of the polarization beam splitter 23.FIG. 23 illustrates an example of spectrum distribution of lightincident on the image pickup device 22, when the bandpass filter 81 isremoved from the configuration and the infrared cut filter 82 isdisposed, in the projection display illustrated in FIG. 20. In FIG. 23,a horizontal axis indicates the wavelength (nm), and a vertical axisindicates the light quantity (a.u.). It is apparent from FIG. 23 thatthe infrared unnecessary light of 800 nm or larger is reduced to a half.Disposing the infrared cut filter 82 is effective at reducing theinfrared unnecessary light included in the illumination light L1.However, the S/N ratio in this state is about 1:5, indicating that thesignal light is still weak and therefore, the detection is difficult.Hence, in the present embodiment a noise component is gradually reducedby using the following combination, so that a high S/N ratio is achievedby combining reduction effects of the respective measures.

Measures against the described components 2 and 3 are as follows. Asillustrated in FIG. 20, the bandpass filter 81, which allows only acertain wavelength region to pass therethrough while cutting wavelengthregions except this range, is disposed in the detection optical system80. FIG. 24 illustrates an example of passband characteristics of thebandpass filter 81. FIG. 25 illustrates an example of spectrumdistribution of light incident on the image pickup device 22, when thebandpass filter 81 is disposed in the detection optical system 80. InFIGS. 24 and 25, a horizontal axis indicates the wavelength (nm), and avertical axis indicates the light quantity (a.u.). FIGS. 24 and 25illustrate characteristics when the bandpass filter 81 having ahalf-value width of 10 nm is inserted. It is apparent that most ofunnecessary light is allowed to be reduced on a smaller wavelength sideand a longer wavelength side than a passband of 785 nm plus/minus 5 nm,and the S/N ratio is allowed to be increased to 4:1. Use of the bandpassfilter 81 makes it possible to create a state in which a signal light isstronger than unnecessary infrared light.

4.2 Configuration Example Suitable for Use of Bandpass Filter 81

Here, a disadvantage that practically occurs and a solution thereto whenthe bandpass filter 81 is used will be discussed.

(Optimization of Placement Position of Bandpass Filter 81)

As illustrated in FIG. 20, a position where the bandpass filter 81 is tobe disposed may be preferably in an optical path provided between thepolarization beam splitter 23 and the first relay lens group 51A andhaving substantial telecentricity. As described above in the thirdembodiment, the image pickup device 22 of the detection system may bepreferably small, in order to build a system that is inexpensive intotal. In that case, it is advisable to build a reduction optical systemby using a relay optical system, and to use the image pickup device 22of a small size. The bandpass filter 81 is configured using a dielectricmultilayer film in many cases, in view of performance. In this case, apassband width shifts at an incident angle of light and therefore,angles of light incident on the bandpass filter 81 may be preferably asclose as possible, so that the bandpass filter 81 serves as a highquality bandpass. Hence, when the bandpass filter 81 is disposed in thedetection optical system 80, if the bandpass filter 81 is at theabove-described position, a chief ray of the detection light issubstantially telecentric and therefore, angles of a light ray grouppassing through the bandpass filter 81 most are the same. For thisreason, an optimum placement position is neither a position between thelenses of the relay optical system nor a position immediately before theimage pickup device 22, but is a position before entrance of thedetection light into the relay optical system. The chief my issubstantially telecentric also in an optical path between the last lens(the second relay lens group 51B) and the image pickup device 22.However, since the reduction optical system is used, Fno becomesbrighter according to a reduction magnification, due to the Lagrangeinvariant relationship. For this reason, concerning light rays exceptthe chief ray, an angle of incident on the bandpass filter 81 increases,which is not desirable.

(Optimization of Passband Width of Bandpass Filter 81)

Although the S/N ratio is drastically improved by inserting the bandpassfilter 81, a disadvantage of making the detection difficult is presentwhen the wavelength of signal light deviates from the band allowed topass therethrough. Next, an optimum value of the passband width will bedescribed as a solution thereto. When a laser light source is used asthe detection light-source section, variability of a laser wavelengthdue to a temperature change depends on a wavelength (a semiconductormaterial). This may be, for example, 0.27 nm/deg C., in a near-infraredlight laser of 783 nm. Assuming that an operating temperature limit ofthe projection display is 0 deg C. to 40 deg C., if a center is a normaltemperature of 25 deg C.,

a low temperature (0 deg C.): 778 nm (785-0.27*(25−0)),

a normal temperature (25 deg C.): 785 nm, and

a high temperature (40 deg C.): 789 nm (785+0.27*(40−25)).

In other words, an emission wavelength of the detection light-sourcesection is 778 nm to 789 nm. In this case, at least 11 nm is necessaryas the passband width of the bandpass filter 81. The necessary bandwidthmay vary depending on a corresponding temperature region, acorresponding wavelength in use, or differences between the individuallaser light sources. However, in order to respond to a temperaturechange in practical use, at least about 10 nm is necessary as thepassband width of the bandpass filter 81. In other words, the bandpassfilter 81 may preferably have a center wavelength same as apredetermined emission wavelength of the detection light-source section,and may preferably have the passband width of 10 nm or more.

(Suppression of Wavelength Variation)

Next, a way of addressing the above-described disadvantage due to thevariation is wavelength by using another technique will be described. Asdescribed above, the emission wavelength of the detection light-sourcesection sensitively varies with temperature. As illustrated in FIG. 26,a suppression section 94 may be provided to suppress this.

The suppression section 94 includes a Peltier device 91 attached to thenear-infrared laser 42, a power supply section 92 connected to thePeltier device 91, and a control section 93 controlling the temperatureof the Peltier device 91 through the power supply section 92. Asillustrated in FIG. 20, the Peltier device 91 is attached in proximityto the near-infrared laser 42 that emits the detection near-infraredlight, to prevent the emission wavelength of the near-infrared laser 42from deteriorating due to an external temperature change. The Peltierdevice 91A may be controlled by a method of managing the temperature.However, the control section 93 may be preferably used to monitor thedetection signal from the image pickup device 22, and to drive thePeltier device 91 so that, for example, a level of the detection signalbecomes highest. This makes it possible to achieve optimization inconsideration of an individual difference that the near-infrared laser42 originally has, unevenness of a maximum passing wave of the bandpassfilter 81, and the like.

(Optimization of Placement Position of Visible-Light Cut Filter 28)

Concerning the placement position of the bandpass filter 81, it has beendescribed that the optimum placement position of the bandpass filter 81may be preferably between the polarization beam splitter 23 and thefirst relay lens group 51A. However, as an adverse effect thereof, thismay involve a decrease in contrast of image display for use asprojector. As described above in the second embodiment, thevisible-light cut filter 28 may be preferably disposed in the detectionoptical system 80, to reduce the visible light reaching the image pickupdevice 22. If prevention of the visible light is the only purpose, thevisible-light cut filter 28 may be disposed immediately before the imagepickup device 22. However, there is a better position for thevisible-light cut filter 28.

The bandpass filter 81 is a dielectric multilayer film and thereforereflects bands other than the passband. Hence, for example, asillustrated in FIG. 27, disposing the bandpass filter 81 in thedetection optical system 80 may cause the bandpass filter 81 to play arole of reflecting the P-polarized component Lp1 of the illumination,light L1 having passed through the polarization beam splitter 23. TheP-polarized component Lp1 reflected by the bandpass filter 81 becomeslight returning to the polarization beam splitter 23, and reflectedtowards the projection lens 24. As a result, the P-polarized componentLp1 is emitted onto the screen, which decreases the contrast of theimage display. Therefore, as illustrated in FIG. 28, the visible-lightcut filter 28 of an absorption type may be preferably disposed betweenthe bandpass filter 81 and the polarization beam splitter 23. This makesit possible to suppress the reflection of the P-polarized component Lp1,and thereby to prevent the contrast from decreasing.

It is to be noted that, in FIGS. 27 and 28, as an example, theP-polarized component Lp1 included in the illumination light L1 is 1%,and the S-polarized component Ls1 is 99%, but the proportion of each ofthese polarized components is not limited to this example.

4.3 Other Preferable Configuration Examples Optimization of InfraredTransmittance of Projection Lens 24

It is possible to improve the S/N ratio, by raising the level of thedetection signal by increasing infrared transmittance of the opticalcomponents through which the detection light passes. In the projectiondisplay of the present embodiment, the detected near-infrared light isincident on the detection optical system 80 through the projection lens24. An ordinary optical component takes care of only a visible range(mainly RGB) and therefore, transmittance in a visible range is kepthigh, which is about 90%. However, in the projection lens 24 of anordinary type, an infrared region is not usually used and therefore isnot taken care of. For example, in a case in which the projection lens24 includes fifteen lens groups like a super short focus lens, when thetransmittance of the infrared region is 90% per group, the transmittanceof the infrared region for the entire projection lens 24 is 0.9¹⁵=21%.On the other hand, by taking care of the infrared region as well, andincreasing the transmittance of the infrared region per group to 97%,the transmittance of the infrared region for the entire projection leas24 becomes 0.97¹⁵=63% and therefore, the transmittance for the entireprojection leas 24 is increased by three times. This allows the level ofthe detection signal to be purely three-fold higher. Therefore, when alens of a super short focus type in which the number of lenses tends tobe large is used for the projection lens 24, it is very important totake care of, in particular, the transmittance of the infrared region ofthe lens.

Based upon the foregoing, when the projection lens 24 is configured of Nlenses (where N is an integer), the transmittance of the projection lens24 for the near-infrared light emitted from the detection light-sourcesection may be preferably (0.95)^(N) or more. The transmittance of theprojection lens 24 may be more preferably (0.97)^(N) or more.

(Optimization of Film Properties of Polarization Beam Splitter 23)

As illustrated in FIG. 29, usually, in order to improve contrastcharacteristics of the visible range, the polarization beam splitter 23may enhance performance of the projector, by being provided with, forexample, film properties of reflecting the S-polarized component andallowing the P polarized light to pass therethrough. In other words,there are provided such properties that, for the illumination light L1,the S-polarized component Ls1 is reflected and the P-polarized componentLp1 is allowed to pass therethrough. However, directly applying theseproperties to the infrared region used for the light detection may notbe preferable. In other words, providing properties of reflecting theS-polarized component Ls3 and allowing the P-polarized component Lp3 topass therethrough for the detection light likewise may not bepreferable. In the first place, the detection light returning to thepolarization beam splitter 23 upon hitting an object such as a finger israndom polarized light scattered by hitting an object like a finger. Forthis reason, when the polarization beam splitter 23 is allowed to haveproperties of allowing the P-polarized-light to pass therethrough, onlya half or less of the light incident on the polarization beam splitter23 as the detection light is allowed to be incident on the detectionoptical system 80. In addition, the infrared light having theP-polarized component included in the illumination light L1 travels intothe detection optical system 80 by passing through the polarization beamsplitter 23.

Therefore, the polarization beam splitter 23 may preferably have filmproperties of reflecting the S-polarized component and allowing theP-polarized component to pass therethrough for the visible light, andfilm properties of reflecting both the S-polarized component and theP-polarized component for the infrared light. This allows, for thedetection light, the S-polarized component Ls3 and the P-polarizedcomponent Lp3 to be reflected by the polarization beam splitter 23towards the detection optical system 80, as illustrated in FIG. 30.Therefore, it is possible to double the proportion of the detectionlight to be incident on the detection optical system 80. In addition, aP-polarized component Lp1 a in the infrared region included in theillumination light L1 is reflected and prevented from traveling to thedetection optical system 80. This reduces a noise component, and servesas measures for an improvement of the S/N ratio.

It is to be noted that, in FIGS. 29 and 30, the P-polarized componentLp1 included in the illumination light L1 is 1%, and the S-polarizedcomponent Ls1 is 99%, but the proportion of each of these polarizedcomponents is not limited thereto.

Other Embodiments

Technology of the present disclosure is not limited to the descriptionof each of the above-described embodiments, and may be variouslymodified.

It is possible to achieve at least the following configurations from theabove-described example embodiments of the disclosure.

(1) A projection display including:

a polarized-light separation device configured to separate incidentlight into a first polarized component and a second polarized component,and to allow the first and the second polarized components to travel inrespective directions different from each other;

an illumination section configured to emit illumination light towardsthe polarized-light separation device, the illumination light includingthe first and the second polarized components, and the first polarizedcomponent being a dominant;

a light valve configured to modulate, based on image data, the firstpolarized component included in the illumination light entering throughthe polarized-light separation device, and to allow the modulated lightto exit therefrom and to pass through the polarized-light separationdevice;

a projection lens configured to project, on a projection plane, themodulated light entering from the light valve through thepolarized-light separation device, and to receive detection lightentering from a direction opposite to a traveling direction of themodulated light;

an image pickup device disposed at a position optically conjugated withthe light valve, and configured to receive the detection light havingentered through both the projection lens and the polarized-lightseparation device; and

one or more optical members disposed between the illumination sectionand the image pickup device, and configured to reduce at least thesecond polarized component included in the illumination light enteringthe image pickup device.

(2) The projection display according to (1), further including an imageprocessing section configured to detect, based on a result ofimage-pickup performed by the image pickup device, a position of afeature point of an object on or in proximity to the projection plane,in a fashion of associating the position with coordinates of a projectedimage on the projection plane.

(3) The projection display according to (1) or (2), wherein the imagepickup device picks up an image in a projection area on the projectionplane, the projection area being formed by the projection lens and beingdefined as an image-pickup area.

(4) The projection display according to any one of (1) to (3), whereinthe one or more optical members includes a polarizing member disposedbetween the illumination section and the polarized-light separationdevice or between the image pickup device and the polarized-lightseparation device, and configured to remove the second polarizedcomponent.

(5) The projection display according to any one of (1) to (3), whereinthe one or more optical members includes a visible-light eat filterdisposed between the polarized-light separation device and the imagepickup device, and configured to reduce a visible light component.

(6) The projection display according to any one of (1) to (5), furtherincluding an illumination control section, wherein

the illumination section includes a first light source, a second lightsource, and a third light source, the first light source beingconfigured to emit light of a first wavelength, the second light sourcebeing configured to emit light of a second wavelength, and the thirdlight source being configured to emit light of a third wavelength,

the illumination control section is configured to control light emissionof each of the first to the third light sources in a field sequentialscheme,

the illumination control section controls light emission to allow afirst light emission period and a second light emission period to beprovided, the first light emission period being a period in which thefirst to the third light sources are allowed to emit light withillumination necessary for image projection, and the second lightemission period being a period in which the first to the third lightsources are allowed to emit light with illumination lower than theillumination in the first light emission period in a range excludingzero illumination, and

the image pickup device picks up an image in the second light emissionperiod.

(7) The projection display according to any one of (1) to (3), furtherincluding a detection light-source section configured to emitnon-visible light for detection, the non-visible light being emitted atleast to cover a non-visible light detection field, and the non-visiblelight detection field being away from the projection plane by apredetermined height and defined by an projection area on the projectionplane formed by the projection lens,

wherein the non-visible light scattered from an object in proximity tothe projection area enters, as the detection light, the image pickupdevice through both the projection lens and the polarized-lightseparation device.

(8) The projection display according to (7), wherein the one or moreoptical members includes a visible-light cut filter disposed between thepolarized-light separation device and the image pickup device, andconfigured to reduce a visible light component.

(9) The projection display according to (8), wherein the one or moreoptical members includes a polarizing member disposed between theillumination section and the polarized-light separation device orbetween the image pickup device and the polarized-light separationdevice, and configured to remove the second polarized component.

(10) The projection display according to any one of (7) to (9), furtherincluding an outer easing having a predetermined surface, andincorporating the detection light-source section,

wherein the projection lens is a super short focus lens with a throwratio of 0.38 or less, and

the outer casing is disposed to allow the predetermined surface to becoplanar with the projection plane.

(11) The projection display according to any one of (7) to (10), wherein

the one or more optical members includes one or more reflecting mirrorsdisposed between the image pickup device and the polarized-lightseparation device, and each having polarization-selectivity andwavelength-selectivity, and

the one or more reflecting mirrors reflects, towards the image pickupdevice, the detection light entering through the projection lens and thepolarized-light separation device.

(12) The projection display according to any one of (1) to (11), furtherincluding one or more relay lens groups disposed between the imagepickup device and the polarized-light separation device, and each havingpositive power.

(13) The projection display according to (12), wherein

the relay lens groups include a first relay lens group and a secondrelay lens group in order from a side close to the polarized-lightseparation device, and

a local length fi of the second relay lens group is smaller than a focallength fb of the first relay lens group.

(14) The projection display according to (13), wherein

the first relay lens group and the second relay lens group form areduction optical system having a reduction magnification B thatsatisfiesB=fi/fb, and

the following is satisfied:Li>B*Lb

where Li is an effective area of an image pickup surface of the imagepickup device, and Lb is an effective area of a display surface of thelight valve.

(15) The projection display according to (7), wherein the one or moreoptical members includes a bandpass filter disposed between thepolarized-light separation device and the image pickup device, andconfigured to allow only light in a specific wavelength region to passtherethrough.

(16) The projection display according to (15), wherein the bandpassfilter has a center wavelength same as a predetermined emissionwavelength of the detection light-source section, and has a passbandwidth of 10 nm or more.

(17) The projection display according to (15) or (16), further includinga suppression section configured to suppress a variation in the emissionwavelength of the detection light-source section, not to exceed apassband width of the bandpass filter.

(18) The projection display according to any one of (15) to (17),further including a telecentric optical system disposed between theimage pickup device and the polarized-light separation device,

wherein the bandpass filter is disposed in an optical path between thetelecentric optical system and the polarized-light separation device,the optical path having substantial telecentricity,

(19) The projection display according to any one of (15) to (18),wherein the one or more optical members includes a visible-light cutfilter disposed between the bandpass filter and the polarized-lightseparation device, and having an absorption property.

(20) The projection display according to any one of (15) to (19),further including an infrared cut filter disposed between theillumination section and the polarized-light separation device,

wherein the detection light-source section emits infrared light as thenon-visible light, and

the infrared cut filter is configured to reduce the infrared light whileallowing visible light to pass therethrough.

(21) The projection display according to any one of (15) to (20),wherein

the detection light-source section emits infrared light as thenon-visible light,

the projection lens includes N lenses where N is an integer, and

transmittance of the projection lens for the infrared light emitted fromthe detection light-source section is (0.95)^(N) or more.

(22) The projection display according to any one of (15) to (21),wherein

the detection light-source section emits infrared light as thenon-visible light, and

the polarized-light separation device has properties of reflecting thefirst polarized component and allowing the second polarized component topass therethrough for visible light, as well as properties of reflectingboth the first and the second polarized components for the infraredlight.

(23) The projection display according to any one of (1) to (22), wherein

the polarized-light separation device allows the first polarizedcomponent included in light from a first direction to travel in a seconddirection, and allows the second polarized component included in thelight entering from the first direction to travel in a third direction,

the illumination section emits the illumination light from the firstdirection, towards the polarized-light separation device,

the light valve modulates, based on image data, the first polarizedcomponent included in the illumination light entering from the seconddirection tough the polarized-light separation device, and allows themodulated light to exit therefrom in a fourth direction and to passthrough the polarized-light separation device,

the projection lens projects, on the projection plane, the modulatedlight entering from the light valve from the fourth direction,

the image pickup device receives the detection light from the thirddirection through both the projection lens and the polarized-lightseparation device, and

the one or more optical members reduces at least the second polarizedcomponent included in the illumination light.

Furthermore, the technology encompasses any possible combination of someor all of the various embodiments described herein and incorporatedherein.

(1) An optical module comprising:

a polarized-light separation device-configured to separate first andsecond polarized components of incident light;

a light valve configured to receive at least the first polarizedcomponent, and output at least a portion of the received light to thepolarized-light separation device;

an imaging device disposed at a position that is at least substantiallyoptically conjugated with the light valve; and

an optical member positioned and configured to remove at least a portionof the second polarized component of the incident light before reachingthe image pickup device.

(2) The optical module according to (1), wherein the light valve isconfigured to modulate at least the first polarized component, andoutput at least a portion of the modulated light to the polarized-lightseparation device.

(3) The optical module according to (1), wherein the polarized-lightseparation device is a wire grid.

(4) The optical module according to (1), wherein the optical member is apolarizer that removes an s-polarized component as the second polarizedcomponent.

(5) The optical module according to (1), wherein the optical member isdisposed between the image device and the polarized-light separationdevice.

(6) The optical module according to (1), wherein the optical member andthe image device are disposed in a first incident light direction.

(7) The optical module according to (6), wherein the light valve isdisposed in a second direction that intersects with the first incidentlight direction.

(8) The optical module according to (1), wherein the polarized-lightseparation device is a polarization beam splitter, and the opticalmember is a polarizer that removes a polarized component as the secondpolarized component.

(9) The optical module according to (1), wherein the polarized-lightseparation device is disposed between the image device and the opticalmember.

(10) The optical module according to (9), wherein the polarized-lightseparation device is a polarization beam splitter, and the opticalmember is a polarizer that removes a polarized component as the secondpolarized component.

(11) The optical module according to (1), further comprising avisible-light filter disposed adjacent to the image device.

(12) The optical module according to (1), wherein the polarized-lightseparation device is disposed between the visible-light filter and theoptical member.

(13) The optical module according to (1), wherein the optical memberincludes a plurality of reflecting mirrors each havingpolarization-selectivity and wavelength-selectivity.

(14) The optical module according to (13), wherein the reflectingmirrors are positioned between a first relay lens group and a secondrelay lens group.

(15) The optical module according to (1), wherein the optical memberincludes at least one of a band-pass filter and a polarizer.

(16) An optical system comprising:

an optical module including

a polarized-light separation device configured to separate first andsecond polarized components of incident light;

a light valve coo figured to receive at least the first polarizedcomponent, and output at least a portion of the received light to thepolarized-light separation device;

an imaging device disposed at a position that is at least substantiallyoptically conjugated with the light valve;

an optical member positioned and configured to remove at least a portionof the second polarized component of the incident light before reachingthe image pickup device; and

an image processing section configured to process image data received bythe image pickup device.

(17) The optical system according to (16), wherein the light valve isconfigured to modulate at least the first polarized component, andoutput at least a portion of the modulated light to the polarized-lightseparation device.

(18) The optical system according to (16), wherein the image processingsection is configured to process image data based on received light thatis outside the visible light spectrum.

(19) The optical system according to (16), further comprising avisible-light filter disposed adjacent to the image device.

(20) A detection method comprising:

separating first and second polarized components of incident light witha polarized-light separation device;

receiving with a light valve at least the first polarized component, andoutputting at least a portion of the received light to thepolarized-light separation device;

projecting an image, based on at least a portion of the modulated light,in a projection path toward a projection area;

receiving with an imaging device at least portions of detection lightthat is incident from the projection area alter the detection lightinteracts with the polarized-light separation device; and

detecting, based on image processing by the image device, a position ofthe object that is positioned in the projection path,

wherein at least a portion of the second polarized component of theincident light is removed by an optical member before reaching the imagepickup device.

(21) The method according to (20), further comprising modulating atleast the first polarized component, and outputting at least a portionof the modulated light to the polarized-light separation device.

(22) The method according to (20), wherein projecting the image anddetecting the position of the object occur simultaneously.

(23) The method according to (20), wherein detecting the position of theobject is based on light detected by the image device that is outsidethe visible light spectrum.

(24) An optical module comprising:

a polarized-light separation device configured to separate first andsecond polarized components of incident light;

a light valve configured to receive at least the first polarizedcomponent, and output at least a portion of the received light to thepolarized-light separation device;

an imaging device disposed at a position that is at least substantiallyoptically conjugated with the light valve; and

an optical member positioned in front of the polarized-light separationdevice.

It should be understood by those skilled in the art that variousmodifications, combinations, subcombinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. An optical module comprising: apolarized-light separation device configured to separate first andsecond polarized components of incident light; a light valve configuredto receive at least the first polarized component, ad output at least aportion of the received light to the polarized-light separation device;an image pickup device disposed at a position that is at leastsubstantially optically conjugated with the light valve; an opticalmember positioned and configured to remove at least a portion of thesecond polarized component of the incident light before reaching theimage pickup device; and a bandpass filter disposed between thepolarized light separation device and the image pickup device, andconfigured to allow only light in a specific wavelength region to passtherethrough.
 2. The optical module according to claim 1, wherein thelight valve is configured to modulate a least the first polarizedcomponent, and output at least a portion it the modulated light to thepolarized-light separation device.
 3. The optical module according toclaim 1, wherein the polarized-light separation device is a wire grid.4. The optical module according to claim 1, wherein the optical memberis a polarized that removes a polarized component as the secondpolarized component.
 5. The optical module according to claim 4, whereinthe polarized-light separation device is a polarization beam splitter.6. The optical module according to claim 1, wherein the optical memberis disposed between the image pickup device and the polarized-lightseparation device.
 7. The optical module according to claim 1, whereinthe optical member and the image pickup device are disposed in a firstincident light direction.
 8. The optical module according to claim 7,wherein the light valve is disposed in a second direction thatintersects with the first incident light direction.
 9. The opticalmodule according to claim 1, wherein the polarized-light separationdevice is disposed between the image pickup device and the opticalmember.
 10. The optical module according to claim 1, further comprisinga visible-light filter disposed adjacent to the image pickup device. 11.The optical module according to claim 10, wherein the polarized-lightseparation device is disposed between the visible-light filter and theoptical member.
 12. The optical module according to claim 1, wherein theoptical member includes a plurality of reflecting mirrors each havingpolarized-selectivity and wavelength-selectivity.
 13. The optical moduleaccording to claim 12, wherein the plurality of reflecting mirrors arepositioned between a first relay lens group and a second relay lensgroup.
 14. The optical module according to claim 1, wherein the opticalmember includes a polarized.
 15. An optical system comprising: anoptical module including a polarized-light separation device configuredto separate first and second polarized components of incident light; alight valve configured to receive at least the first polarizedcomponent, and output at least a portion of the received light to thepolarized-light separation device; an image pickup device disposed at aposition that is at least substantially optically conjugated with the itvalve; an optical member positioned and configured to remove at least aportion of the second polarized component of the incident light beforereaching the image pickup device; a bandpass filter disposed between thepolarized-light separation device and the image pickup device, andconfigured to allow only light in a specific wavelength region to passtherethrough; and an image processing section configured to processimage data received by the image pickup device.
 16. The optical systemaccording to claim 15, wherein the light valve is configured to modulateat least the first polarized component, and output at least a portion ofthe modulated light to the polarized-light separation device.
 17. Theoptical system according to claim 15, wherein the image processingsection is configured to process the image data based on received lightthat is outside a visible light spectrum.
 18. The optical systemaccording to claim 15, further comprising a visible-light filterdisposed adjacent to the image pickup device.
 19. A detection methodcomprising: separating first and second polarized components of incidentlight with a polarizing-light separation device; receiving with a lightvalve at least the first polarized component, and outputting at least aportion of the received light to the polarized-light separation device;projecting an image, based on at least a portion of the received light,in a projection path toward a projection area; allowing, with a bandpassfilter disposed between the polarized-light separation device and animage pickup device, only light in a specific wavelength region to passthrough the bandpass filter before reaching the image pickup device;receiving with the image pickup device at least portions of detectionlight that is incident from the projection area after the detectionlight interacts with the polarized-light separation device; anddetecting, based an image processing by the image pickup device, aposition of an object that is positioned in the projection path, whereinat least a portion of the second polarized component of the incidentlight is removed by an optical member before reaching the image pickupdevice.
 20. The method according to claim 19, further comprisingmodulating at least the first polarized component, and outputting atleast a portion of the modulated light to the polarized-light separationdevice.
 21. The method according to claim 19, wherein projecting theimage and detecting the position of the object occur simultaneously. 22.The method according to claim 19, wherein detecting the position of theobject is based on light detected by the image pickup device that isoutside a visible light spectrum.
 23. An optical module comprising: apolarized-light separation device configured to separate first andsecond polarized components of incident light; a light valve configuredto receive at least the first polarized component, and output at least aportion of the received light to the polarized-light separation device;an image pickup device disposed at a position that is at leastsubstantially optically conjugated with the light valve; an opticalmember positioned in front of the polarized-light separation device; anda bandpass filter disposed between the polarized-light separation deviceand the image pickup device, and configured to allow only light in aspecific wavelength region to pass therethrough.